This invention relates in general to apparatus and processes for fabricating flexible belts.
Various techniques have been devised to form belts from webs. Thermoplastic webs may be joined by overlapping the edge of one web over another and placing the overlapped or seam portion of the webs over a base beneath an ultrasonic vibrating welding element. The technique of ultrasonic welding of thermoplastic material is well known and illustrated, for example, in U.S. Pat. No. 4,532,166, U.S. Pat. No. 3,879,256, U.S. Pat. No. 3,939,033, U.S. Pat. No. 3,947,307 and U.S. Pat. No. 3,459,610, all incorporated by reference herein in their entirety.
Unfortunately, batch processes for cutting and welding webs into belts require considerable time, duplicate manual handling, occupy excessive floor space and also require extensive equipment for alignment, cutting, welding trimming and other processing steps. Also, excessive manual handling increases the likelihood of damage to sensitive substrates or coatings, particularly for coated substrates that must meet precise tolerance requirements such as flexible electrostatographic imaging members including photoreceptors for high speed electrostatographic copiers, duplicators, printers and the like. Scratches and even fingerprints on the vulnerable surfaces of a sensitive, flexible photoreceptor renders the photoreceptor unacceptable for most electrostatographic copiers, duplicators and printers.
Also, when multiply batch handling techniques are utilized to fabricate belts, it is also often difficult to achieve uniform belt conicity and uniform quality. Moreover, because of differences in belt size requirements for different electrostatographic copiers, duplicators, printers and the like, a machine suitable for fabricating a belt of one diameter or width cannot be readily used to prepare a belt of a different diameter or width without encountering delays and expense. Further, lap joints formed with the leading edge over the trailing edge cannot be readily changed with the trailing edge over the leading edge for new batches where one side of a belt differs from the other side.
Automatic systems for fabricating belts has been created that overcome many of the problems encountered with manual or multiple batch belt making techniques. For example, an automatic system is described in U.S. Pat No. 4,838,964 and U.S. Pat. No. 4,878,985. Although many good belts may be fabricated with this system, it has been found that many belts produced by this system have a welded seam that is not uniformly flat. This non-uniformity can adversely affect electrophotographic imaging performance in high speed monochrome and color copiers, duplicators and printers which demand precise tolerances throughout the belt, including the seam area. Non-uniformity at the seam region of a belt can be readily observed with the naked eye and is most visible when stresses exist in the seam. Under this condition, the seam will exhibit a non-flat surface of unacceptable quality. When the seam of a belt exhibits this non-uniformity, it can, during image cycling, cause uneven transfer of toner from the photoreceptor to paper. Uneven application of toner results in dark and light printable areas which extend from the seam. Scrapping of poor quality electrophotographic imaging belts can significantly affect manufacturing yields.